Non-invasive nerve stimulation

ABSTRACT

One example provides a nerve stimulation treatment using electrodes coupled to a user. Examples determine a target charge level and output a series of pulses from the electrodes. For each pulse outputted, examples measure a charge value of the pulse and compare the charge value to the target charge level. If the charge value is greater than the target charge level, examples reduce a strength level of a subsequent outputted pulse. If the charge value is less than the target charge level, examples increase the strength level of a subsequent outputted pulse.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]This application claims priority of U.S. Provisional PatentApplication Ser. No. 62/582,634, filed on Nov. 7, 2017, and claimspriority as a continuation-in-part application of U.S. patentapplication Ser. No. 15/040,856, filed on Feb. 10, 2016, which claimspriority to U.S. Provisional Patent Application Ser. No. 62/115,607,filed Feb. 12, 2015 and claims priority as a continuation-in-partapplication of U.S. patent application Ser. No. 14/893,946, filed onNov. 25, 2015, which claims priority to PCT Patent Application SerialNo. PCT/US14/40240, filed May 30, 2014, which claims priority to U.S.Provisional Patent Application Ser. No. 61/828,981, filed May 30, 2013.The disclosure of each of these applications is hereby incorporated byreference.

FIELD

One example is directed generally to a nerve stimulation, and inparticular to nerve stimulation using electrical signals with computercontrol.

BACKGROUND INFORMATION

Mammalian and human nerves control organs and muscles. Artificiallystimulating the nerves elicit desired organ and muscle responses.Accessing the nerves to selectively control these responses from outsidethe body, without invasive implants or needles penetrating the dermis,muscle or fat tissue, is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a depiction of a neuron activating a muscle by electricalimpulse.

FIG. 2 is a representation of the electrical potential activation timeof an electrical impulse in a nerve.

FIG. 3 is a graph showing pulses applied to the skin.

FIG. 4 is a graph showing symmetrical and asymmetrical pulses applied tothe skin.

FIG. 5 is a cross-sectional diagram showing a field in underlying tissueproduced by application of two electrodes to the skin.

FIG. 6 is a cross-sectional diagram showing a field in underlying tissueproduced by application of two electrodes to the skin, with two layersof tissue of different electrical resistivity.

FIG. 7 is a cross-sectional diagram showing a field in underlying tissuewhen the stimulating pulse is turned off.

FIG. 8 shows potential applications of electrical stimulation to thebody.

FIG. 9A is a system diagram of an example software and hardwarecomponents showing an example of a Topical Nerve Stimulator/Sensor(TNSS) interpreting a data stream from a control device in accordancewith one example.

FIG. 9B is a flow chart showing an example of a function of a mastercontrol program in accordance with one example.

FIG. 10 is a block diagram of an example TNSS component configurationincluding a system on a chip (SOC) in accordance with one example.

FIG. 11 is a flow diagram of the protocol for adaptive current controlin accordance with one example.

FIG. 12 is a Differential Integrator Circuit used in the AdaptiveCurrent Protocol in accordance with one example.

FIG. 13 is a table relating charge duration vs. frequency to providefeedback to the Adaptive Current Protocol in accordance with oneexample.

DETAILED DESCRIPTION

One example is a non-invasive nerve stimulator that uses feedback toadapt the nerve stimulation output. One example is implemented using aTopical Nerve Stimulator and Sensor (“TNSS”) device such as disclosed inU.S. patent application Ser. No. 14/893,946, hereby incorporated byreference, and that is used to stimulate nerves. A TNSS may applyelectrode-generated electric field(s) in a low frequency to dermis inthe proximity of a nerve, and typically applies such a field in themagnitude of up to 100s of hertz (“Hz”). The TNSS also includes hardwareand logic for high frequency (“GHz”) communication to mobile devices.

A wireless system including a TNSS device is disclosed herein. Itscomponents, features and performance characteristics are set forth inthe following technical description. Advantages of a wireless TNSSsystem over existing transcutaneous electrical nerve stimulation devicesinclude: (1) fine control of all stimulation parameters from a remotedevice such as a smartphone, either directly by the user or by storedprograms; (2) multiple electrodes of a TNSS can form an array to shapean electric field in the tissues; (3) multiple TNSS devices can form anarray to shape an electric field in the tissues; (4) multiple TNSSdevices can stimulate multiple structures, coordinated by a smartphone;(5) selective stimulation of nerves and other structures at differentlocations and depths in a volume of tissue; (6) mechanical, acoustic oroptical stimulation in addition to electrical stimulation; (7) thetransmitting antenna of TNSS device can focus a beam of electromagneticenergy within tissues in short bursts to activate nerves directlywithout implanted devices; (8) inclusion of multiple sensors of multiplemodalities, including but not limited to position, orientation, force,distance, acceleration, pressure, temperature, voltage, light and otherelectromagnetic radiation, sound, ions or chemical compounds, making itpossible to sense electrical activities of muscles (EMG, EKG),mechanical effects of muscle contraction, chemical composition of bodyfluids, location or dimensions or shape of an organ or tissue bytransmission and receiving of ultrasound.

Further advantages of the wireless TNSS system include: (1) TNSS devicesare expected to have service lifetimes of days to weeks and theirdisposability places less demand on power sources and batteryrequirements; (2) the combination of stimulation with feedback fromartificial or natural sensors for closed loop control of musclecontraction and force, position or orientation of parts of the body,pressure within organs, and concentrations of ions and chemicalcompounds in the tissues; (3) multiple TNSS devices can form a networkwith each other, with remote controllers, with other devices, with theInternet and with other users; (4) a collection of large amounts of datafrom one or many TNSS devices and one or many users regarding sensingand stimulation, collected and stored locally or through the internet;(5) analysis of large amounts of data to detect patterns of sensing andstimulation, apply machine learning, and improve algorithms andfunctions; (6) creation of databases and knowledge bases of value; (7)convenience, including the absence of wires to become entangled inclothing, showerproof and sweat proof, low profile, flexible,camouflaged or skin colored, (8) integrated power, communications,sensing and stimulating inexpensive disposable TNSS, consumableelectronics; (9) power management that utilizes both hardware andsoftware functions will be critical to the convenience factor andwidespread deployment of TNSS device.

Referring to FIG. 1, a nerve cell normally has a voltage across the cellmembrane of 70 millivolts with the interior of the cell at a negativevoltage with respect to the exterior of the cell. This is known as theresting potential and it is normally maintained by metabolic reactionswhich maintain different concentrations of electrical ions in the insideof the cell compared to the outside. Ions can be actively “pumped”across the cell membrane through ion channels in the membrane that areselective for different types of ion, such as sodium and potassium. Thechannels are voltage sensitive and can be opened or closed depending onthe voltage across the membrane. An electric field produced within thetissues by a stimulator can change the normal resting voltage across themembrane, either increasing or decreasing the voltage from its restingvoltage.

Referring to FIG. 2, a decrease in voltage across the cell membrane toabout 55 millivolts opens certain ion channels, allowing ions to flowthrough the membrane in a self-catalyzing but self-limited process whichresults in a transient decrease of the trans membrane potential to zero,and even positive, known as depolarization followed by a rapidrestoration of the resting potential as a result of active pumping ofions across the membrane to restore the resting situation which is knownas repolarization. This transient change of voltage is known as anaction potential and it typically spreads over the entire surface of thecell. If the shape of the cell is such that it has a long extensionknown as an axon, the action potential spreads along the length of theaxon. Axons that have insulating myelin sheaths propagate actionpotentials at much higher speeds than those axons without myelin sheathsor with damaged myelin sheaths.

If the action potential reaches a junction, known as a synapse, withanother nerve cell, the transient change in membrane voltage results inthe release of chemicals known as neuro-transmitters that can initiatean action potential in the other cell. This provides a means of rapidelectrical communication between cells, analogous to passing a digitalpulse from one cell to another.

If the action potential reaches a synapse with a muscle cell it caninitiate an action potential that spreads over the surface of the musclecell. This voltage change across the membrane of the muscle cell opension channels in the membrane that allow ions such as sodium, potassiumand calcium to flow across the membrane, and can result in contractionof the muscle cell.

Increasing the voltage across the membrane of a cell below −70millivolts is known as hyper-polarization and reduces the probability ofan action potential being generated in the cell. This can be useful forreducing nerve activity and thereby reducing unwanted symptoms such aspain and spasticity

The voltage across the membrane of a cell can be changed by creating anelectric field in the tissues with a stimulator. It is important to notethat action potentials are created within the mammalian nervous systemby the brain, the sensory nervous system or other internal means. Theseaction potentials travel along the body's nerve “highways”. The TNSScreates an action potential through an externally applied electric fieldfrom outside the body. This is very different than how action potentialsare naturally created within the body.

Electric Fields that can Cause Action Potentials

Referring to FIG. 2, electric fields capable of causing actionpotentials can be generated by electronic stimulators connected toelectrodes that are implanted surgically in close proximity to thetarget nerves. To avoid the many issues associated with implanteddevices, it is desirable to generate the required electric fields byelectronic devices located on the surface of the skin. Such devicestypically use square wave pulse trains of the form shown in FIG. 3. Suchdevices may be used instead of implants and/or with implants such asreflectors, conductors, refractors, or markers for tagging target nervesand the like, so as to shape electric fields to enhance nerve targetingand/or selectivity.

Referring to FIG. 3, the amplitude of the pulses “A”, applied to theskin, may vary between 1 and 100 Volts, pulse width “t”, between 100microseconds and 10 milliseconds, duty cycle (t/T) between 0.1% and 50%,the frequency of the pulses within a group between 1 and 100/sec, andthe number of pulses per group “n”, between 1 and several hundred.Typically, pulses applied to the skin will have an amplitude of up to 60volts, a pulse width of 250 microseconds and a frequency of 20 persecond, resulting in a duty cycle of 0.5%. In some cases balanced-chargebiphasic pulses will be used to avoid net current flow. Referring toFIG. 4, these pulses may be symmetrical, with the shape of the firstpart of the pulse similar to that of the second part of the pulse, orasymmetrical, in which the second part of the pulse has lower amplitudeand a longer pulse width in order to avoid canceling the stimulatoryeffect of the first part of the pulse.

Formation of Electric Fields by Stimulators

The location and magnitude of the electric potential applied to thetissues by electrodes provides a method of shaping the electrical field.For example, applying two electrodes to the skin, one at a positiveelectrical potential with respect to the other, can produce a field inthe underlying tissues such as that shown in the cross-sectional diagramof FIG. 5.

The diagram in FIG. 5 assumes homogeneous tissue. The voltage gradientis highest close to the electrodes and lower at a distance from theelectrodes. Nerves are more likely to be activated close to theelectrodes than at a distance. For a given voltage gradient, nerves oflarge diameter are more likely to be activated than nerves of smallerdiameter. Nerves whose long axis is aligned with the voltage gradientare more likely to be activated than nerves whose long axis is at rightangles to the voltage gradient.

Applying similar electrodes to a part of the body in which there are twolayers of tissue of different electrical resistivity, such as fat andmuscle, can produce a field such as that shown in FIG. 6. Layers ofdifferent tissue may act to refract and direct energy waves and be usedfor beam aiming and steering. An individual's tissue parameters may bemeasured and used to characterize the appropriate energy stimulation fora selected nerve.

Referring to FIG. 7, when the stimulating pulse is turned off theelectric field will collapse and the fields will be absent as shown. Itis the change in electric field that will cause an action potential tobe created in a nerve cell, provided sufficient voltage and the correctorientation of the electric field occurs. More complex three-dimensionalarrangements of tissues with different electrical properties can resultin more complex three-dimensional electric fields, particularly sincetissues have different electrical properties and these properties aredifferent along the length of a tissue and across it, as shown in Table1.

TABLE 1 Electrical Conductivity (siemens/m) Direction Average Blood .65Bone Along .17 Bone Mixed .095 Fat .05 Muscle Along .127 Muscle Across.45 Muscle Mixed .286 Skin (Dry) .000125 Skin (Wet) .00121

Modification of Electric Fields by Tissue

An important factor in the formation of electric fields used to createaction potentials in nerve cells is the medium through which theelectric fields must penetrate. For the human body this medium includesvarious types of tissue including bone, fat, muscle, and skin. Each ofthese tissues possesses different electrical resistivity or conductivityand different capacitance and these properties are anisotropic. They arenot uniform in all directions within the tissues. For example, an axonhas lower electrical resistivity along its axis than perpendicular toits axis. The wide range of conductivities is shown in Table 1. Thethree-dimensional structure and resistivity of the tissues willtherefore affect the orientation and magnitude of the electric field atany given point in the body.

Modification of Electric Fields by Multiple Electrodes

Applying a larger number of electrodes to the skin can also produce morecomplex three-dimensional electrical fields that can be shaped by thelocation of the electrodes and the potential applied to each of them.Referring to FIG. 3, the pulse trains can differ from one anotherindicated by A, t/T, n, and f as well as have different phaserelationships between the pulse trains. For example with an 8×8 array ofelectrodes, combinations of electrodes can be utilized ranging fromsimple dipoles, to quadripoles, to linear arrangements, to approximatelycircular configurations, to produce desired electric fields withintissues.

Applying multiple electrodes to a part of the body with complex tissuegeometry will thus result in an electric field of a complex shape. Theinteraction of electrode arrangement and tissue geometry can be modeledusing Finite Element Modeling, which is a mathematical method ofdividing the tissues into many small elements in order to calculate theshape of a complex electric field. This can be used to design anelectric field of a desired shape and orientation to a particular nerve.

High frequency techniques known for modifying an electric field, such asthe relation between phases of a beam, cancelling and reinforcing byusing phase shifts, may not apply to application of electric fields byTNSSs because they use low frequencies. Instead, examples use beamselection to move or shift or shape an electric field, also described asfield steering or field shaping, by activating different electrodes,such as from an array of electrodes, to move the field. Selectingdifferent combinations of electrodes from an array may result in beam orfield steering. A particular combination of electrodes may shape a beamand/or change the direction of a beam by steering. This may shape theelectric field to reach a target nerve selected for stimulation.

Activation of Nerves by Electric Fields

Typically, selectivity in activating nerves has required electrodes tobe implanted surgically on or near nerves. Using electrodes on thesurface of the skin to focus activation selectively on nerves deep inthe tissues, as with examples of the invention, has many advantages.These include avoidance of surgery, avoidance of the cost of developingcomplex implants and gaining regulatory approval for them, and avoidanceof the risks of long-term implants.

The features of the electric field that determine whether a nerve willbe activated to produce an action potential can be modeledmathematically by the “Activating Function” disclosed in Rattay F., “Thebasic mechanism for the electrical stimulation of the nervous system”,Neuroscience Vol. 89, No. 2, pp. 335-346 (1999). The electric field canproduce a voltage, or extracellular potential, within the tissues thatvaries along the length of a nerve. If the voltage is proportional todistance along the nerve, the first order spatial derivative will beconstant and the second order spatial derivative will be zero. If thevoltage is not proportional to distance along the nerve, the first orderspatial derivative will not be constant and the second order spatialderivative will not be zero. The Activating Function is proportional tothe second-order spatial derivative of the extracellular potential alongthe nerve. If it is sufficiently greater than zero at a given point itpredicts whether the electric field will produce an action potential inthe nerve at that point. This prediction may be input to a nervesignature.

In practice, this means that electric fields that are varyingsufficiently greatly in space or time can produce action potentials innerves. These action potentials are also most likely to be producedwhere the orientation of the nerves to the fields change, either becausethe nerve or the field changes direction. The direction of the nerve canbe determined from anatomical studies and imaging studies such as MRIscans. The direction of the field can be determined by the positions andconfigurations of electrodes and the voltages applied to them, togetherwith the electrical properties of the tissues. As a result, it ispossible to activate certain nerves at certain tissue locationsselectively while not activating others.

To accurately control an organ or muscle, the nerve to be activated mustbe accurately selected. This selectivity may be improved by usingexamples disclosed herein as a nerve signature, in several ways, asfollows:

-   -   (1) Improved algorithms to control the effects when a nerve is        stimulated, for example, by measuring the resulting electrical        or mechanical activity of muscles and feeding back this        information to modify the stimulation and measuring the effects        again. Repeated iterations of this process can result in        optimizing the selectivity of the stimulation, either by        classical closed loop control or by machine learning techniques        such as pattern recognition and artificial intelligence;    -   (2) Improving nerve selectivity by labeling or tagging nerves        chemically; for example, introduction of genes into some nerves        to render them responsive to light or other electromagnetic        radiation can result in the ability to activate these nerves and        not others when light or electromagnetic radiation is applied        from outside the body;    -   (3) Improving nerve selectivity by the use of electrical        conductors to focus an electric field on a nerve; these        conductors might be implanted, but could be passive and much        simpler than the active implantable medical devices currently        used;    -   (4) The use of reflectors or refractors, either outside or        inside the body, is used to focus a beam of electromagnetic        radiation on a nerve to improve nerve selectivity. If these        reflectors or refractors are implanted, they may be passive and        much simpler than the active implantable medical devices        currently used;    -   (5) Improving nerve selectivity by the use of feedback from the        person upon whom the stimulation is being performed; this may be        an action taken by the person in response to a physical        indication such as a muscle activation or a feeling from one or        more nerve activations;    -   (6) Improving nerve selectivity by the use of feedback from        sensors associated with the TNSS, or separately from other        sensors, that monitor electrical activity associated with the        stimulation; and    -   (7) Improving nerve selectivity by the combination of feedback        from both the person or sensors and the TNSS that may be used to        create a unique profile of the user's nerve physiology for        selected nerve stimulation.

Potential applications of electrical stimulation to the body are shownin FIG. 8.

Referring to FIG. 9A, a TNSS 934 human and mammalian interface and itsmethod of operation and supporting system are managed by a MasterControl Program (“MCP”) 910 represented in function format as blockdiagrams. It provides the logic for the nerve stimulator system inaccordance to one example.

In one example, MCP 910 and other components shown in FIG. 9A areimplemented by one or more processors that are executing instructions.The processor may be any type of general or specific purpose processor.Memory is included for storing information and instructions to beexecuted by the processor. The memory can be comprised of anycombination of random access memory (“RAM”), read only memory (“ROM”),static storage such as a magnetic or optical disk, or any other type ofcomputer readable media.

Master Control Program

The primary responsibility of MCP 910 is to coordinate the activitiesand communications among the various control programs, a Data Manager920, a User 932, and the external ecosystem and to execute theappropriate response algorithms in each situation. The MCP 910accomplishes electric field shaping and/or beam steering by providing anelectrode activation pattern to TNSS device 934 to selectively stimulatea target nerve. For example, upon notification by a CommunicationsController 930 of an external event or request, the MCP 910 isresponsible for executing the appropriate response, and working with theData Manager 920 to formulate the correct response and actions. Itintegrates data from various sources such as Sensors 938 and externalinputs such as TNSS devices 934, and applies the correct security andprivacy policies, such as encryption and HIPAA required protocols. Itwill also manage the User Interface (UI) 912 and the various ApplicationProgram Interfaces (APIs) 914 that provide access to external programs.

MCP 910 is also responsible for effectively managing power consumptionby TNSS device 934 through a combination of software algorithms andhardware components that may include, among other things: computing,communications, and stimulating electronics, antenna, electrodes,sensors, and power sources in the form of conventional or printedbatteries.

Communications Controller

Communications controller 930 is responsible for receiving inputs fromthe User 932, from a plurality of TNSS devices 934, and from 3rd partyapps 936 via communications sources such as the Internet or cellularnetworks. The format of such inputs will vary by source and must bereceived, consolidated, possibly reformatted, and packaged for the DataManager 920.

User inputs may include simple requests for activation of TNSS devices934 to status and information concerning the User's 932 situation orneeds. TNSS devices 934 will provide signaling data that may includevoltage readings, TNSS 934 status data, responses to control programinquiries, and other signals. Communications Controller 930 is alsoresponsible for sending data and control requests to the plurality ofTNSS devices 934. 3rd party applications 936 can send data, requests, orinstructions for the Master Control Program 910 or User 932 via theInternet or cellular networks. Communications Controller 930 is alsoresponsible for communications via the cloud where various softwareapplications may reside.

In one example, a user can control one or more TNSS devices using aremote fob or other type of remote device and a communication protocolsuch as Bluetooth. In one example, a mobile phone is also incommunication and functions as a central device while the fob and TNSSdevice function as peripheral devices. In another example, the TNSSdevice functions as the central device and the fob is a peripheraldevice that communicates directly with the TNSS device (i.e., a mobilephone or other device is not needed).

Data Manager

The Data Manager (DM) 920 has primary responsibility for the storage andmovement of data to and from the Communications Controller 930, Sensors938, Actuators 940, and the Master Control Program 910. The DM 920 hasthe capability to analyze and correlate any of the data under itscontrol. It provides logic to select and activate nerves. Examples ofsuch operations upon the data include: statistical analysis and trendidentification; machine learning algorithms; signature analysis andpattern recognition, correlations among the data within the DataWarehouse 926, the Therapy Library 922, the Tissue Models 924, and theElectrode Placement Models 928, and other operations. There are severalcomponents to the data that is under its control as disclosed below.

The Data Warehouse (DW) 926 is where incoming data is stored; examplesof this data can be real-time measurements from TNSS devices 934 or fromSensors (938), data streams from the Internet, or control andinstructional data from various sources. The DM 920 will analyze data,as described above, that is held in the DW 926 and cause actions,including the export of data, under MCP 910 control. Certain decisionmaking processes implemented by the DM 920 will identify data patternsboth in time, frequency, and spatial domains and store them assignatures for reference by other programs. Techniques such as EMG, ormulti-electrode EMG, gather a large amount of data that is the sum ofhundreds to thousands of individual motor units and the typicalprocedure is to perform complex decomposition analysis on the totalsignal to attempt to tease out individual motor units and theirbehavior. The DM 920 will perform big data analysis over the totalsignal and recognize patterns that relate to specific actions or evenindividual nerves or motor units. This analysis can be performed overdata gathered in time from an individual, or over a population of TNSSUsers.

The Therapy Library 922 contains various control regimens for the TNSSdevices 934. Regimens specify the parameters and patterns of pulses tobe applied by the TNSS devices 934. The width and amplitude ofindividual pulses may be specified to stimulate nerve axons of aparticular size selectively without stimulating nerve axons of othersizes. The frequency of pulses applied may be specified to modulate somereflexes selectively without modulating other reflexes. There are presetregimens that may be loaded from the Cloud 942 or 3rd party apps 936.The regimens may be static read-only as well as adaptive with read-writecapabilities so they can be modified in real-time responding to controlsignals or feedback signals or software updates. Referring to FIG. 3,one such example of a regimen has parameters A=40 volts, t=500microseconds, T=1 Millisecond, n=100 pulses per group, and f=20 persecond. Other examples of regimens will vary the parameters withinranges previously specified.

The Tissue Models 924 are specific to the electrical properties ofparticular body locations where TNSS devices 934 may be placed. Aspreviously disclosed, electric fields for production of actionpotentials will be affected by the different electrical properties ofthe various tissues that they encounter. Tissue Models 924 are combinedwith regimens from the Therapy Library 922 and Electrode PlacementModels 928 to produce desired actions. Tissue Models 924 may bedeveloped by MRI, Ultrasound or other imaging or measurement of tissueof a body or particular part of a body. This may be accomplished for aparticular User 932 and/or based upon a body norm. One such example of adesired action is the use of a Tissue Model 924 together with aparticular Electrode Placement Model 928 to determine how to focus theelectric field from electrodes on the surface of the body on a specificdeep location corresponding to the pudendal nerve in order to stimulatethat nerve selectively to reduce incontinence of urine. Other examplesof desired actions may occur when a Tissue Model 924 in combination withregimens from the Therapy Library 22 and Electrode Placement Models 928produce an electric field that stimulates a sacral nerve. Many otherexamples of desired actions follow for the stimulation of other nerves.

Electrode Placement Models 928 specify electrode configurations that theTNSS devices 934 may apply and activate in particular locations of thebody. For example, a TNSS device 934 may have multiple electrodes andthe Electrode Placement Model 928 specifies where these electrodesshould be placed on the body and which of these electrodes should beactive in order to stimulate a specific structure selectively withoutstimulating other structures, or to focus an electric field on a deepstructure. An example of an electrode configuration is a 4 by 4 set ofelectrodes within a larger array of multiple electrodes, such as an 8 by8 array. This 4 by 4 set of electrodes may be specified anywhere withinthe larger array such as the upper right corner of the 8 by 8 array.Other examples of electrode configurations may be circular electrodesthat may even include concentric circular electrodes. The TNSS device934 may contain a wide range of multiple electrodes of which theElectrode Placement Models 928 will specify which subset will beactivated. The Electrode Placement Models 928 complement the regimens inthe Therapy Library 922 and the Tissue Models 924 and are used togetherwith these other data components to control the electric fields andtheir interactions with nerves, muscles, tissues and other organs. Otherexamples may include TNSS devices 934 having merely one or twoelectrodes, such as but not limited to those utilizing a closed circuit.

Sensor/Actuator Control

Independent sensors 938 and actuators 940 can be part of the TNSSsystem. Its functions can complement the electrical stimulation andelectrical feedback that the TNSS devices 934 provide. An example ofsuch a sensor 938 and actuator 940 include, but are not limited to, anultrasonic actuator and an ultrasonic receiver that can providereal-time image data of nerves, muscles, bones, and other tissues. Otherexamples include electrical sensors that detect signals from stimulatedtissues or muscles. The Sensor/Actuator Control module 950 provides theability to control both the actuation and pickup of such signals, allunder control of the MCP 910.

Application Program Interfaces

The MCP 910 is also responsible for supervising the various ApplicationProgram Interfaces (APIs) that will be made available for 3rd partydevelopers. There may exist more than one API 914 depending upon thespecific developer audience to be enabled. For example many statisticalfocused apps will desire access to the Data Warehouse 926 and itscumulative store of data recorded from TNSS 934 and User 932 inputs.Another group of healthcare professionals may desire access to theTherapy Library 922 and Tissue Models 924 to construct better regimensfor addressing specific diseases or disabilities. In each case adifferent specific API 914 may be appropriate.

The MCP 910 is responsible for many software functions of the TNSSsystem including system maintenance, debugging and troubleshootingfunctions, resource and device management, data preparation, analysis,and communications to external devices or programs that exist on thesmart phone or in the cloud, and other functions. However, one of itsprimary functions is to serve as a global request handler taking inputsfrom devices handled by the Communications Controller 930, externalrequests from the Sensor Control Actuator Module (950), and 3rd partyrequests 936. Examples of High Level Master Control Program (MCP)functions are disclosed below.

The manner in which the MCP handles these requests is shown in FIG. 9B.The Request Handler (RH) 960 accepts inputs from the User 932, TNSSdevices 934, 3rd party apps 936, sensors 938 and other sources. Itdetermines the type of request and dispatches the appropriate responseas set forth in the following paragraphs.

User Request: The RH 960 will determine which of the plurality of UserRequests 961 is present such as: activation; display status,deactivation, or data input, e.g. specific User condition. Shown in FIG.9B is the RH's 960 response to an activation request. As shown in block962, RH 960 will access the Therapy Library 922 and cause theappropriate regimen to be sent to the correct TNSS 934 for execution, asshown at block 964 labeled “Action.”

TNSS/Sensor Inputs: The RH 960 will perform data analysis over TNSS 934or Sensor inputs 965. As shown at block 966, it employs data analysis,which may include techniques ranging from DSP decision making processes,image processing algorithms, statistical analysis and other algorithmsto analyze the inputs. In FIG. 9B two such analysis results are shown;conditions which cause a User Alarm 970 to be generated and conditionswhich create an Adaptive Action 980 such as causing a control feedbackloop for specific TNSS 934 functions, which can iteratively generatefurther TNSS 934 or Sensor inputs 965 in a closed feedback loop.

3rd Party Apps: Applications can communicate with the MCP 910, bothsending and receiving communications. A typical communication would beto send informational data or commands to a TNSS 934. The RH 960 willanalyze the incoming application data, as shown at block 972. FIG. 9Bshows two such actions that result. One action, shown at block 974 wouldbe the presentation of the application data, possibly reformatted, tothe User 932 through the MCP User Interface 912. Another result would beto perform a User 932 permitted action, as shown at 976, such asrequesting a regimen from the Therapy Library 922.

Referring to FIG. 10, an example TNSS in accordance to one example isshown. The TNSS has one or more electronic circuits or chips 1000 thatperform the functions of: communications with the controller, nervestimulation via one or more electrodes 1008 that produce a wide range ofelectric field(s) according to treatment regimen, one or more antennae1010 that may also serve as electrodes and communication pathways, and awide range of sensors 1006 such as, but not limited to, mechanicalmotion and pressure, temperature, humidity, chemical and positioningsensors. In another example, TNSS interfaces to transducers 1014 totransmit signals to the tissue or to receive signals from the tissue.

One arrangement is to integrate a wide variety of these functions intoan SOC, system on chip 1000. Within this is shown a control unit 1002for data processing, communications, transducer interface and storageand one or more stimulators 1004 and sensors 1006 that are connected toelectrodes 1008. An antenna 1010 is incorporated for externalcommunications by the control unit. Also present is an internal powersupply 1012, which may be, for example, a battery. An external powersupply is another variation of the chip configuration. It may benecessary to include more than one chip to accommodate a wide range ofvoltages for data processing and stimulation. Electronic circuits andchips will communicate with each other via conductive tracks within thedevice capable of transferring data and/or power.

The TNSS interprets a data stream from the control device, such as thatshown in FIG. 9A, to separate out message headers and delimiters fromcontrol instructions. In one example, control instructions containinformation such as voltage level and pulse pattern. The TNSS activatesthe stimulator 1004 to generate a stimulation signal to the electrodes1008 placed on the tissue according to the control instructions. Inanother example the TNSS activates a transducer 1014 to send a signal tothe tissue. In another example, control instructions cause informationsuch as voltage level and pulse pattern to be retrieved from a librarystored in the TNSS.

The TNSS receives sensory signals from the tissue and translates them toa data stream that is recognized by the control device, such as theexample in FIG. 9A. Sensory signals include electrical, mechanical,acoustic, optical and chemical signals among others. Sensory signalscome to the TNSS through the electrodes 1008 or from other inputsoriginating from mechanical, acoustic, optical, or chemical transducers.For example, an electrical signal from the tissue is introduced to theTNSS through the electrodes 1008, is converted from an analog signal toa digital signal and then inserted into a data stream that is sentthrough the antenna 1010 to the control device. In another example anacoustic signal is received by a transducer 1014 in the TNSS, convertedfrom an analog signal to a digital signal and then inserted into a datastream that is sent through the antenna 1010 to the control device. Incertain examples sensory signals from the tissue are directly interfacedto the control device for processing.

An open loop protocol to control current to electrodes in known neuralstimulation devices does not have feedback controls. It commands avoltage to be set, but does not check the actual Voltage. Voltagecontrol is a safety feature. A stimulation pulse is sent based on presetparameters and cannot be modified based on feedback from the patient'sanatomy. When the device is removed and repositioned, the electrodeplacement varies. Also the humidity and temperature of the anatomychanges throughout the day. All these factors affect the actual chargedelivery if the voltage is preset.

In contrast, examples of the TNSS stimulation device have features thataddress these shortcomings using the Nordic Semiconductor nRF52832microcontroller to regulate charge in a TNSS. The High Voltage Supply isimplemented using a LED driver chip combined with a Computer controlledDigital Potentiometer to produce a variable voltage. A 3-1 step upTransformer then provides the desired High Voltage, “VBOOST”, which issampled to assure that no failure causes an incorrect Voltage level asfollows. The nRF52832 Microcontroller samples the voltage of thestimulation waveform providing feedback and impedance calculations foran adaptive protocol to modify the waveform in real time. The Currentdelivered to the anatomy by the stimulation waveform is integrated usinga differential integrator and sampled and then summed to determineactual charge delivered to the user for a Treatment. After every pulsein a Stimulation event, this measurement is analyzed and used to modify,in real time, subsequent pulses.

This hardware adaptation allows a firmware protocol to implement theadaptive protocol. This protocol regulates the charge applied to thebody by changing VBOOST. A treatment is performed by a sequence ofperiodic pulses, which insert charge into the body through theelectrodes. Some of the parameters of the treatment are fixed and someare user adjustable. The strength, duration and frequency may be useradjustable. The user may adjust these parameters as necessary forcomfort and efficacy. The strength may be lowered if there is discomfortand raised if nothing is felt. The duration will be increased if themaximum acceptable strength results in an ineffective treatment.

A flow diagram in accordance with one example of the Adaptive Protocoldisclosed above is shown in FIG. 11. The Adaptive Protocol strives torepeatedly and reliably deliver a target charge (“Q_(target)”) during atreatment and to account for any environmental changes. Therefore, thefunctionality of FIG. 11 is to adjust the charge level applied to a userbased on feedback, rather than use a constant level.

The mathematical expression of this protocol is as follows:Q_(target)=Q_(target)(A*dS+B*dT), where A is the StrengthCoefficient—determined empirically, dS is the user change in Strength, Bis the Duration Coefficient—determined empirically, and dT is the userchange in Duration.

The Adaptive Protocol includes two phases in one example: Acquisition1100 and Reproduction 1120. Any change in user parameters places theAdaptive Protocol in the Acquisition phase. When the first treatment isstarted, a new baseline charge is computed based on the new parameters.At a new acquisition phase at 1102, all data from the previous chargeapplication is discarded. In one example, 1102 indicates the first timefor the current usage where the user places the TNSS device on a portionof the body and manually adjusts the charge level, which is a series ofcharge pulses, until it feels suitable, or any time the charge level ischanged, either manually or automatically. The treatment then starts.The mathematical expression of this function of the application of acharge is as follows: The charge delivered in a treatment is

$Q_{target} = {\sum\limits_{i = 1}^{T*f}{Q_{pulse}(i)}}$

Where T is the duration; f is the frequency of “Rep Rate”; Q_(pulse)(i)is the measured charge delivered by Pulse (i) in the treatment pulsetrain provided as a voltage MON_CURRENT that is the result of aDifferential Integrator circuit shown in FIG. 12 (i.e., the averageamount of charge per pulse). The Nordic microcontroller of FIG. 12 is anexample of an Analog to Digital Conversion feature used to quantifyvoltage into a number representing the delivered charge and thereforedetermine the charge output. The number of pulses in the treatment isT*f.

At 1104 and 1106, every pulse is sampled. In one example, thefunctionality of 1104 and 1106 lasts for 10 seconds with a pulse rate of20 Hz, which can be considered a full treatment cycle. The result ofphase 1100 is the target pulse charge of Q_(target).

FIG. 13 is a table in accordance with one example showing the number ofpulses per treatment measured against two parameters, frequency andduration. Frequency is shown on the Y-axis and duration on the X-axis.The Adaptive Current protocol in general performs better when using morepulses. One example uses a minimum of 100 pulses to provide for solidconvergence of charge data feedback. Referring to the FIG. 13, afrequency setting of 20 Hz and duration of 10 seconds produces 200pulses, which is desirable to allow the Adaptive Current Protocol toreproduce a previous charge.

The reproduction phase 1120 begins in one example when the userinitiates another subsequent treatment after acquisition phase 1100 andthe resulting acquisition of the baseline charge, Q_(target). Forexample, a full treatment cycle, as discussed above, may take 10seconds. After, for example, a two-hour pause as shown at wait period1122, the user may then initiate another treatment. During this phase,the Adaptive Current Protocol attempts to deliver Q_(target) for eachsubsequent treatment. The functionality of phase 1120 is needed because,during the wait period 1122, conditions such as the impedance of theuser's body due to sweat or air humidity may have changed. Thedifferential integrator is sampled at the end of each Pulse in theTreatment. At that point, the next treatment is started and thedifferential integrator is sampled for each pulse at 1124 for purposesof comparison to the acquisition phase Q_(target). Sampling the pulseincludes measuring the output of the pulse in coulombs.

The output of the integrator of FIG. 12 in voltage, referred to asMon_Current 1201, is a direct linear relationship to the deliveredcharge in micro-coulombs and provides a reading of how much charge isleaving the device and entering the user. At 1126, each single pulse iscompared to the charge value determined in phase 1100 (i.e., the targetcharge) and the next pulse will be adjusted in the direction of thedifference.

NUM_PULSES=(T*f)

After each pulse, the observed charge, Q_(pulse)(i), is compared to theexpected charge per pulse.

Q _(pulse)(i)>Q _(target/)NUM_PULSES?

The output charge or “VBOOST” is then modified at either 1128(decreasing) or 1130 (increasing) for the subsequent pulse by:

dV(i)=G[Q _(target)/NUM_PULSES−Q _(pulse)(i)]

where G is the Voltage adjustment Coefficient—determined empirically.The process continues until the last pulse at 1132.

A safety feature assures that the VBOOST will never be adjusted higherby more than 10%. If more charge is necessary, then the repetition rateor duration can be increased.

In one example, in general, the current is sampled for every pulseduring acquisition phase 1100 to establish target charge forreproduction. The voltage is then adjusted via a digital potentiometer,herein referred to as “Pot”, during reproduction phase 1120 to achievethe established target_charge.

The digital Pot is calibrated with the actual voltage at startup. Atable is generated with sampled voltage for each wiper value. Tables arealso precomputed storing the Pot wiper increment needed for 1v and 5voutput delta at each pot level. This enables quick reference for voltageadjustments during the reproduction phase. The tables may need periodicrecalibration due to battery level.

In one example, during acquisition phase 1100, the minimum data set=100pulses and every pulse is sampled and the average is used as thetarget_charge for reproduction phase 1120. In general, less than 100pulses may provide an insufficient data sample to use as a basis forreproduction phase 1120. In one example, the default treatment is 200pulses (i.e., 20 Hz for 10 seconds). In one example, a user can adjustboth duration and frequency manually.

In one example, during acquisition phase 1100, the maximum data set=1000pulses. The maximum is used to avoid overflow of 32 bit integers inaccumulating the sum of samples. Further, 1000 pulses in one example isa sufficiently large data set and collecting more is likely unnecessary.

After 1000 pulses for the above example, the target_charge is computed.Additional pulses beyond 1000 in the acquisition phase do not contributeto the computation of the target charge.

In one example, the first 3-4 pulses are generally higher than the restso these are not used in acquisition phase 1100. This is also accountedfor in reproduction phase 1120. Using these too high values can resultin target charge being set too high and over stimulating on thesubsequent treatments in reproduction phase 1120. In other examples,more advanced averaging algorithms could be applied to eliminating highand low values.

In an example, there may be a safety concern about automaticallyincreasing the voltage. For example, if there is poor connection betweenthe device and the user's skin, the voltage may auto-adjust at 1130 upto the max. The impedance may then be reduced, for example by the userpressing the device firmly, which may result in a sudden high current.Therefore, in one example, if the sample is 500 mv or more higher thanthe target, it immediately adjusts to the minimum voltage. This examplethen remains in reproduction phase 1120 and should adjust back to thetarget current/charge level. In another example, the maximum voltageincrease is set for a single treatment (e.g., 10V). More than thatshould not be needed in normal situations to achieve the establishedtarget_charge. In another example, a max is set for VBOOST (e.g., 80V).

In various examples, it is desired to have stability during reproductionphase 1120. In one example, this is accomplished by adjusting thevoltage by steps. However, a relatively large step adjustment can resultin oscillation or over stimulation. Therefore, voltage adjustments maybe made in smaller steps. The step size may be based on both the deltabetween the target and sample current as well as on the actual VBOOSTvoltage level. This facilitates a quick and stable/smooth convergence tothe target charge and uses a more gradual adjustments at lower voltagesfor more sensitive users.

The following are the conditions that may be evaluated to determine theadjustment step.

-   -   delta-mon_current=abs(sample_mon_current−target_charge)    -   If delta_mon_current>500 mv and VBOOST>20V then step=5V for        increase adjustments    -   (For decrease adjustments a 500 mv delta triggers emergency        decrease to minimum Voltage)    -   If delta_mon_current>200 mv then step=1V    -   If delta_mon_current>100 mv and        delta_mon_current>5%*sample_mon_current then step=1V

In other examples, new treatments are started with voltage lower thantarget voltage with a voltage buffer of approximately 10%. The impedanceis unknown at the treatment start. These examples save thetarget_voltage in use at the end of a treatment. If the user has notadjusted the strength parameter manually, it starts a new treatment withsaved target_voltage with the 10% buffer. This achieves target currentquickly with the 10% buffer to avoid possible over stimulation in caseimpedance has been reduced. This also compensates for the first 3-4pulses that are generally higher.

As disclosed, examples apply an initial charge level, and thenautomatically adjust based on feedback of the amount of current beingapplied. The charge amount can be varied up or down while being applied.Therefore, rather than setting and then applying a fixed voltage levelthroughout a treatment cycle, implementations of the invention measurethe amount of charge that is being input to the user, and adjustaccordingly throughout the treatment to maintain a target charge levelthat is suitable for the current environment.

Several examples are specifically illustrated and/or described herein.However, it will be appreciated that modifications and variations of thedisclosed examples are covered by the above teachings and within thepurview of the appended claims without departing from the spirit andintended scope of the invention.

What is claimed is:
 1. A method of providing a nerve stimulationtreatment using electrodes coupled to a user, the method comprising:determining a target charge level; outputting a series of pulses fromthe electrodes; for each pulse outputted, measuring a charge value ofthe pulse and compare the charge value to the target charge level; ifthe charge value is greater than the target charge level, reducing astrength level of a subsequent outputted pulse; and if the charge valueis less than the target charge level, increasing the strength level of asubsequent outputted pulse.
 2. The method of claim 1, in which theseries of pulses are defined based on a frequency and a duration.
 3. Themethod of claim 1, in which determining the target charge levelQ_(target) comprises generating an acquisition series of pulses and${Q_{target} = {\sum\limits_{i = 1}^{T*f}{Q_{pulse}(i)}}},$ where T isa duration of the acquisition series of pulses, f is a frequency of theacquisition series of pulses and Q_(pulse)(i) is a measured charge ofeach of the acquisition series of pulses.
 4. The method of claim 1, inwhich the measuring the charge value of the pulse comprises determiningan output of a differential integrator.
 5. The method of claim 1, inwhich the series of pulses comprises at least 100 pulses.
 6. The methodof claim 1, in which an amount of the reducing the strength andincreasing the strength is limited by a predefined step value.
 7. Themethod of claim 1, in which the determining the target charge leveloccurs after a manual adjustment of a voltage output level.
 8. A nervestimulation device comprising: one or more electrodes; one or moresensors; a processor coupled to the electrodes and the sensors, theprocessor executing instructions to implement nerve stimulationcomprising: determining a target charge level; outputting a series ofpulses from the electrodes; for each pulse outputted, measuring at thesensors a charge value of the pulse and compare the charge value to thetarget charge level; if the charge value is greater than the targetcharge level, reducing a strength level of a subsequent outputted pulse;and if the charge value is less than the target charge level, increasingthe strength level of a subsequent outputted pulse.
 9. The nervestimulation device of claim 8, in which the series of pulses are definedbased on a frequency and a duration.
 10. The nerve stimulation device ofclaim 8, in which determining the target charge level Q_(target)comprises generating an acquisition series of pulses and${Q_{target} = {\sum\limits_{i = 1}^{T*f}{Q_{pulse}(i)}}},$ where T isa duration of the acquisition series of pulses, f is a frequency of theacquisition series of pulses and Q_(pulse)(i) is a measured charge ofeach of the acquisition series of pulses.
 11. The nerve stimulationdevice of claim 8, in which the measuring the charge value of the pulsecomprises determining an output of a differential integrator.
 12. Thenerve stimulation device of claim 8, in which the series of pulsescomprises at least 100 pulses.
 13. The nerve stimulation device of claim8, in which an amount of the reducing the strength and increasing thestrength is limited by a predefined step value.
 14. The nervestimulation device of claim 8, in which the determining the targetcharge level occurs after a manual adjustment of a voltage output level.15. A non-transitory computer-readable medium having instructions storedthereon that, when executed by a processor, cause the processor toprovide a nerve stimulation treatment using electrodes coupled to auser, the nerve stimulation treatment comprising: determining a targetcharge level; outputting a series of pulses from the electrodes; foreach pulse outputted, measuring a charge value of the pulse and comparethe charge value to the target charge level; if the charge value isgreater than the target charge level, reducing a strength level of asubsequent outputted pulse; and if the charge value is less than thetarget charge level, increasing the strength level of a subsequentoutputted pulse.
 16. The non-transitory computer-readable medium ofclaim 15, in which the series of pulses are defined based on a frequencyand a duration.
 17. The non-transitory computer-readable medium of claim15, in which determining the target charge level Q_(target) comprisesgenerating an acquisition series of pulses and${Q_{target} = {\sum\limits_{i = 1}^{T*f}{Q_{pulse}(i)}}},$ where T isa duration of the acquisition series of pulses, f is a frequency of theacquisition series of pulses and Q_(pulse)(i) is a measured charge ofeach of the acquisition series of pulses.
 18. The non-transitorycomputer-readable medium of claim 15, in which the measuring the chargevalue of the pulse comprises determining an output of a differentialintegrator.
 19. The non-transitory computer-readable medium of claim 15,in which the series of pulses comprises at least 100 pulses.
 20. Thenon-transitory computer-readable medium of claim 15, in which an amountof the reducing the strength and increasing the strength is limited by apredefined step value.
 21. The non-transitory computer-readable mediumof claim 15, in which the determining the target charge level occursafter a manual adjustment of a voltage output level.